Experts always talk about eating in a calorie deficit to lose weight, but dipping too low can also be an issue. Without enough food for survival (including our normal daily functions), your body will send signals to conserve calories, slowing down your metabolism, explained registered dietitian and CSCS-certified trainer Lisa Bunn. "While calorie deficit is a must for weight loss, the nuance is that we don't want it to be too much of a deficit."
Bunn explained that without enough food for survival, our bodies will start shutting down and use muscle tissue for energy instead of fat stores. Aim for a moderate calorie deficit, not a major one, to avoid extreme hunger, which could result in binge eating. When creating a calorie deficit, never dip below 1,200 calories a day.
The difference between being in a calorie deficit and a calorie surplus (losing vs. gaining weight) can be a few hundred calories, Lisa explained, so she recommended tracking food to accurately calculate what you're eating. Again, you can set these daily calorie target goals with a registered dietitian or by using this formula.